In high-speed inkjet systems with high-tension webs, the substrate may experience significant stretching and distortion as a result of the absorption of the ink while the web is under tension. For example, when the web is paper, the distortion and stretching causes noticeable image distortion errors between the color planes of a multi-component system. With some inkjet systems, the resulting image distortion has caused significant customer satisfaction problems, and (along with other significant factors) has led some customers to reserve the printer for one-component printing. Furthermore, drying of the ink during processing causes the paper to shrink, and subsequent component printing causes the paper to stretch again. Stretching may be different in the “scan” direction (i.e., perpendicular to the direction of travel of the web) than in the “process” direction (i.e., the direction of travel of the web) because of the tension in the web. Since the ink content of the components can differ greatly, the degree of stretching or distortion may differ between printing stations.
Conventional inkjet systems have had significant problems with web distortion, which have been addressed mechanically with custom unwinders. The custom unwinder is costly, but its primary shortcoming is that it is not part of a closed-loop system. Specifically, the unwinder does not measure local stretching of the web and adjust its work appropriately.
Furthermore, the unwinder works at only the entry point of the system, so that non-uniform distortion along the process direction cannot be addressed.
Accordingly, what is needed is a system and method for overcoming the above-identified problems. The present invention addresses such a need.